Subject: Re:large disk platters? - test-drb@ccmp.vtda.org

22 Feb 2003

Wow !

Tony, could you send some photos of your disk drive ?
I'd like to see this "mystical" thing ! :)
The 24" platters of IBM's RAMAC are known to me but 36" platters ???
Who could have built such disk drives ? Any ideas of the company ?

Pierre

...
   In about 1976
University of Missouri Bioengineering Program acquired an "IBM
 surplus image system" from somebody "unknown" out west.  They sent a
couple  
 [...]

  There were two clamshell halves that were opened
to access the platter, each
 track had a fixed head over it.  Stored on each track was the image on a
 single display station.  By switching between tracks you could access
 different images.  There was a vacuum pump to remove the air if you opened
 the clamshells to adjust the heads.  Each of the display stations had an
 integrated keyboard and a proximity or optical pen to select menu items.    
 One of the peripherals I have for my PDP11s is a PPL model 121 display 
 system.

 It uses a magnentic disk to store the video images. I think it rotates 
 once per field (the motor speed is electronically controlled with an eddy 
 current brake IIRC). Images are stored using analogue FM modulation on 3 
 tracks of the disk (one for each of R, G, B). There are several sets of 
 fixed heads which can be selected so you can store several images on the 
 disk and display them.

 The disk is a lot smaller than the ones described here, though. I've not 
 taken the HDA apat (for obvious reasons), but it looks to be a normal 14" 
 platter. The HDA fits, disk horizontal, into a normal 19" rack module. 
 There's a separate PSU rack module, and a cardcage of electronics. It 
 connects to the Unibus via a DR11B interface I think.

 -tony 

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